Temperature control device for optoelectronic devices

ABSTRACT

Current may be passed through an n-doped semiconductor region, a recessed metal semiconductor alloy portion, and a p-doped semiconductor region so that the diffusion of majority charge carriers in the doped semiconductor regions transfers heat from or into the semiconductor waveguide through Peltier-Seebeck effect. Further, a temperature control device may be configured to include a metal semiconductor alloy region located in proximity to an optoelectronic device, a first semiconductor region having a p-type doping, and a second semiconductor region having an n-type doping. The temperature of the optoelectronic device may thus be controlled to stabilize the performance of the optoelectronic device.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/363,995, filed Feb. 1, 2012, which is a divisional of U.S. patentapplication Ser. No. 12/498,463, filed Jul. 7, 2009, now U.S. Pat. No.8,111,724, the entire contents and disclosures of which is incorporatedherein by reference.

BACKGROUND

The present invention relates to a semiconductor structure, andparticularly to a temperature control device for an optoelectronicdevice and a germanium photodetector for silicon waveguide, and methodsof manufacturing the same, and methods of operating the same.

A semiconductor waveguide may be employed in microphotonic devices toenable high efficiency long range transmission of light over distancesin the micrometer range or in the millimeter range. The semiconductorwaveguide typically employs a single crystalline semiconductor materialto minimize signal loss due to absorption of light. The semiconductormaterial in the semiconductor waveguide has a relative high refractiveindex. For example, silicon and germanium have a refractive index ofabout 3.45 and about 4.0, respectively. A dielectric material having alower refractive constant surrounds the semiconductor waveguide so thata total reflection condition is satisfied at the interface between thesemiconductor waveguide and the dielectric material for light impingingon the interface at a glancing angle. The semiconductor wave guide maythus be employed to transmit light having a wavelength greater than thewavelength corresponding to the band gap of the semiconductor material.Typically, infrared lights are employed in the semiconductor waveguide.

Many microphotonic devices manipulate the light in the semiconductorwaveguide in some way. For example, the light in the semiconductorwaveguide may be absorbed, reflected, or induced to change the phase.Many of the prior art methods that accomplish such optical manipulationemploy exotic materials or special processing steps that are nottypically employed in standard complementary metal-oxide-semiconductor(CMOS) processing steps, thereby increasing the manufacturing cost andprocessing complexity.

In view of the above, there exists a need to provide a structure thatmanipulates the light in a semiconductor waveguide with standard CMOSprocessing steps, and methods of manufacturing the same. Particularly,there exists a need to provide a structure that modulates the phase ofthe light in the semiconductor waveguide with standard CMOS processingsteps, and methods of manufacturing the same.

Further, performance of many optoelectronic devices is temperaturesensitive. For example, performance of a semiconductor laser device issignificantly affected by temperature variation. In a semiconductor chipintegrating conventional semiconductor devices and optoelectronicdevices, the performance of optoelectronic devices may be affectedsignificantly due to the heat generated by conventional semiconductordevices and transferred to the optoelectronic devices. Thus, it isnecessary to stabilize the temperature of the optoelectronic devices toprovide stable operation of the optoelectronic devices within thesemiconductor chip.

While placing optoelectronic devices at a location far away from theconventional semiconductor devices the thermal effect on the performanceof the optoelectronic devices, such a design lowers the areal density ofthe conventional semiconductor devices or the optoelectronic devices.Thus, an integrated semiconductor chip including conventionalsemiconductor devices and optoelectronic devices at high density withoutadverse impact on the performance of the optoelectronic devices due tothe thermal effects on the optoelectronic devices is desired.

BRIEF SUMMARY

The present invention provides a semiconductor waveguide having anintegrated thermoelectric temperature control device to enable phaseshifting of the light in the semiconductor waveguide and anoptoelectronic device having an integrated thermoelectric temperaturecontrol device to control the temperature of the optoelectronic device.

In one embodiment of the present invention, a semiconductor waveguide isformed integrally with non-recessed semiconductor regions that areadjoined to the semiconductor waveguide through a recessed semiconductorportion having a lesser thickness than the semiconductor waveguide. Oneof the non-recessed semiconductor portions and an adjoining region ofthe recessed semiconductor portion are doped with p-type dopants to forma p-doped semiconductor region, and another of the non-recessedsemiconductor portions and an adjoining region of the recessessemiconductor portion are doped with n-type dopants to form an n-dopedsemiconductor region. After forming a dielectric spacer that coverssidewalls of the p-doped semiconductor region and the n-dopedsemiconductor region, the recessed semiconductor portion is metallizedto form a recessed metal semiconductor alloy portion. Current is passedthrough the n-doped semiconductor region, the recessed metalsemiconductor alloy portion, and the p-doped semiconductor region. Thediffusion of majority charge carriers in the doped semiconductor regionstransfers heat from or into the semiconductor waveguide throughPeltier-Seebeck effect. The temperature change in the semiconductorwaveguide alters refractive index of the semiconductor waveguide, whichmay be employed to modulate the phase of the light passing through thesemiconductor waveguide.

According to an aspect of the present invention, a semiconductorstructure is provided, which comprises:

a semiconductor waveguide having a first thickness and located on a topsurface of an insulator layer;

a recessed semiconductor region of integral construction with thesemiconductor waveguide, having a second thickness that is less than thefirst thickness, located on the insulator layer, and including asubstantially undoped recessed semiconductor region;

a p-doped semiconductor region laterally abutting the substantiallyundoped recessed semiconductor region;

an n-doped semiconductor region laterally abutting the substantiallyundoped recessed semiconductor region and not abutting the p-dopedsemiconductor region; and

a recessed metal semiconductor alloy portion abutting the recessedsemiconductor region, the p-doped semiconductor region, and the n-dopedsemiconductor region.

According to another aspect of the present invention, a method offorming a semiconductor structure is provided, which comprises:

forming shallow trench isolation structures laterally abutting a topsemiconductor portion and vertically abutting a buried insulator layerin a top semiconductor layer of a semiconductor-on-insulator (SOI)substrate;

forming a semiconductor waveguide by patterning the top semiconductorportion;

forming a p-doped semiconductor region in the top semiconductor portion;

forming an n-doped semiconductor region not abutting the p-dopedsemiconductor region in the top semiconductor region; and

forming a recessed metal semiconductor alloy portion directly on arecessed region of the top semiconductor portion, wherein the recessedmetal semiconductor alloy portion is formed directly on the p-dopedsemiconductor region and the n-doped semiconductor region.

According to yet another aspect of the present invention, a method ofoperating a semiconductor device is provided, which comprises:

providing a semiconductor structure including:

-   -   a semiconductor waveguide located on a top surface of an        insulator layer;    -   a p-doped semiconductor region thermally connected to the        silicon waveguide;    -   an n-doped semiconductor region thermally connected to the        silicon waveguide and not abutting the p-doped semiconductor        region; and    -   a recessed metal semiconductor alloy portion abutting the        p-doped semiconductor region and the n-doped semiconductor        region; and

passing current through the n-doped semiconductor region, the recessedmetal semiconductor alloy portion, and the p-doped semiconductor region.

In another embodiment of the present invention, an optoelectronic deviceis formed on a semiconductor substrate in proximity to a temperaturecontrol device. A semiconductor waveguide that is optically coupled tothe optoelectronic device may be formed to enable transmission ofoptical signal through the semiconductor waveguide. The temperaturecontrol device is configured to include a metal semiconductor alloyregion located in proximity to the optoelectronic device, a firstsemiconductor region having a p-type doping, and a second semiconductorregion having an n-type doping. The metal semiconductor alloy region isthermally coupled with the optoelectronic device. Electrical current maybe caused to flow through the first semiconductor region, the metalsemiconductor alloy region, and the second semiconductor region to allowcooling of the metal semiconductor alloy region and the optoelectronicdevice through heat transfer. Conversely, the current may be caused toflow in the opposite direction to allow heating of the metalsemiconductor alloy region and the optoelectronic device through heattransfer. The temperature of the optoelectronic device may thus becontrolled to stabilize the performance of the optoelectronic device.

According to an aspect of the present invention, a semiconductorstructure including a temperature control device and an optoelectronicdevice is provided. The temperature control device includes: a firstmetal semiconductor alloy region located on a substrate; a p-dopedsemiconductor portion abutting the first metal semiconductor alloyregion and located on the substrate; an n-doped semiconductor portionabutting the first metal semiconductor alloy region located on thesubstrate; wherein the temperature control device is configured to passcurrent from the p-doped semiconductor portion, through the first metalsemiconductor alloy region, and to the n-doped semiconductor portion orfrom the n-doped semiconductor portion, through the first metalsemiconductor alloy region, and to the p-doped semiconductor portion.The optoelectronic device includes a device that comprises asemiconductor material, configured to manipulate electromagneticradiation, and is thermally coupled to the temperature control device.

According to another aspect of the present invention, a method offorming a semiconductor structure including a temperature control deviceand an optoelectronic device is provided. The method includes:patterning a top semiconductor layer of a semiconductor-on-insulatorsubstrate to form a p-doped semiconductor portion and an n-dopedsemiconductor portion; forming a first metal semiconductor alloy regiondirectly on the p-doped semiconductor portion and the n-dopedsemiconductor portion, wherein the p-doped semiconductor portion and ann-doped semiconductor portion and the first metal semiconductor alloyregion constitute a portion of a temperature control device; forming acurrent conduction path configured to pass current from the p-dopedsemiconductor portion, through the first metal semiconductor alloyregion, and to the n-doped semiconductor portion or from the n-dopedsemiconductor portion, through the first metal semiconductor alloyregion, and to the p-doped semiconductor portion; and forming anoptoelectronic device comprising a semiconductor material, configured tomanipulate electromagnetic radiation, and is thermally coupled to thetemperature control device.

According to yet another aspect of the present invention, a method ofoperating a semiconductor structure comprising a temperature controldevice and an optoelectronic device is provided. The method includes:providing a temperature control device including a first metalsemiconductor alloy region located on a substrate, a p-dopedsemiconductor portion abutting the first metal semiconductor alloyregion and located on the substrate, and an n-doped semiconductorportion abutting the first metal semiconductor alloy region located onthe substrate; providing an optoelectronic device including a devicethat comprises a semiconductor material, configured to manipulateelectromagnetic radiation, and is thermally coupled to the temperaturecontrol device; and passing electrical current from the p-dopedsemiconductor portion, through the first metal semiconductor alloyregion, and to the n-doped semiconductor portion or from the n-dopedsemiconductor portion, through the first metal semiconductor alloyregion, and to the p-doped semiconductor portion, wherein heat istransferred in the direction of flow of majority charge carriers in thep-doped semiconductor portion and the n-doped semiconductor portion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For all of the figures herein, the following conventions apply. Figureswith the same numeric label correspond to the same stage ofmanufacturing for an exemplary semiconductor structure. Within FIGS.1A-9C, figures with the suffix “A” are top-down views, and figures withthe suffix “B” or “C” are horizontal cross-sectional views along theplane B-B′ or the plane C-C′, respectively, in the figure with the samenumeric label and the suffix “A.”

FIGS. 1A-1C are various views of a first exemplary semiconductorstructure corresponding to the step after formation of a shallow trenchisolation structures 34.

FIGS. 2A-2C are various views of the first exemplary semiconductorstructure corresponding to the step after formation of a pair ofrecessed line trenches 31.

FIGS. 3A-3C are various views of the first exemplary semiconductorstructure corresponding to the step after removal of a first photoresist(37A, 37B, 37C).

FIGS. 4A-4C are various views of the first exemplary semiconductorstructure corresponding to the step after formation of p-dopedsemiconductor regions (46A, 46B).

FIGS. 5A-5C are various views of the first exemplary semiconductorstructure corresponding to the step after formation of n-dopedsemiconductor regions (48A, 48B).

FIGS. 6A-6C are various views of the first exemplary semiconductorstructure corresponding to the step after removal of a third photoresist47.

FIGS. 7A-7C are various views of the first exemplary semiconductorstructure corresponding to the step after formation of a dielectricmaterial layer 60L.

FIGS. 8A-8C are various views of the first exemplary semiconductorstructure corresponding to the step after formation of a dielectricmaterial portion 62 and dielectric spacers 64.

FIGS. 9A-9C are various views of the first exemplary semiconductorstructure corresponding to the step after formation of various metalsemiconductor alloy portions, a middle-of-line (MOL) dielectric layer80, and various conductive contact vias.

FIGS. 10, 11, and 12A, 12B, 13A, 13B, 14A, 14B, 15A, 15B, 16A, and 16Bare various views of a second exemplary semiconductor structurecorresponding to a second embodiment of the present invention. FIGS. 10and 11 are vertical cross-sectional views. Each of FIGS. 12A, 13A, 13A,14A, 15A, and 16A is a vertical cross-sectional view along a verticalplane labeled Z-Z′ in figures with the numeric label and the suffix “B.”FIGS. 11B, 12B, 13B, and 14B are top-down views. FIG. 15B is a top-downview of selected elements to demonstrate lateral geometricalrelationship between the selected elements.

FIG. 17 is a vertical cross-sectional view of a third exemplarysemiconductor structure.

FIG. 18 is a vertical cross-sectional view of a fourth exemplarysemiconductor structure.

FIG. 19 is a vertical cross-sectional view of a fifth exemplarysemiconductor structure.

FIGS. 20 and 21 are sequential vertical cross-sectional views of a sixthexemplary semiconductor structure.

FIG. 22 is a top-down view of selected elements to demonstrate lateralgeometrical relationship between the selected elements of a seventhexemplary semiconductor structure according to a seventh embodiment ofthe present invention.

DETAILED DESCRIPTION

As stated above, the present invention relates to a temperature controldevice for an optoelectronic device and a germanium photodetector forsilicon waveguide, and methods of manufacturing the same, and methods ofoperating the same, which are now described in detail with accompanyingfigures. Throughout the drawings, the same reference numerals or lettersare used to designate like or equivalent elements. Detailed descriptionsof known functions and constructions unnecessarily obscuring the subjectmatter of the present invention have been omitted for clarity. Thedrawings are not necessarily drawn to scale.

Referring to FIGS. 1A-1F, an exemplary semiconductor structure accordingto the present invention comprises a semiconductor substrate, which is asemiconductor-on-insulator (SOI) substrate. The semiconductor substrateincludes an insulator layer 20 and a top semiconductor layer locatedabove the insulator layer 20. The semiconductor substrate may furtherinclude a handle substrate 10, which is attached to the bottom surfaceof the insulator layer 20. The handle substrate 10 may comprise asemiconductor material, an insulator material, a conductive material, ora combination thereof. The insulator layer 20 and the handle substrate10, if present, provide structural support to the top semiconductorlayer which may comprise a contiguous semiconductor material layer thatcovers the entirety of the insulator layer 20.

The contiguous semiconductor material layer comprises a semiconductormaterial. Exemplary semiconductor materials that may be employed for thecontiguous semiconductor material layer include, but are not limited to,silicon, germanium, silicon-germanium alloy, silicon carbon alloy,silicon-germanium-carbon alloy, gallium arsenide, indium arsenide,indium phosphide, III-V compound semiconductor materials, II-VI compoundsemiconductor materials, organic semiconductor materials, and othercompound semiconductor materials. Preferably, the entirety of thecontiguous semiconductor material layer comprises a single crystallinesemiconductor material having an epitaxial alignment among thesemiconductor atoms. For example, the semiconductor material of thecontiguous semiconductor material layer may comprise single crystallinesilicon or single crystalline germanium. The thickness of the contiguoussemiconductor material layer, which is herein referred to as a firstthickness t1, may be from about 50 nm to about 1,000 nm, and typicallyfrom about 200 nm to about 500 nm, although lesser and greaterthicknesses can also be employed.

Preferably, the contiguous semiconductor material layer comprises asubstantially undoped semiconductor material so that the amount ofimpurities, including dopant atoms, in the contiguous semiconductormaterial layer is minimized. By minimizing the amount of impurities inthe contiguous material layer, a semiconductor waveguide to besubsequently formed from a portion of the contiguous material layerprovides low absorption rate of the signal. The atomic concentration ofimpurities, including dopants, in the contiguous semiconductor materiallayer is less than about 1.0×10¹⁶/cm³, and preferably less than about1.0×10¹⁵/cm³, and more preferably less than about 1.0×10¹⁴/cm³. In casethe contiguous semiconductor material layer comprises silicon, theresistivity of the material of the contiguous semiconductor materiallayer is greater than about 1 Ohm-cm, and preferably greater than about10 Ohm-cm, and more preferably greater than about 100 Ohm-cm.

Trenches extending to the top surface of the insulator layer 20 areformed within the contiguous semiconductor material layer by acombination of lithographic means and an etch. Specifically, aphotoresist (not shown) is applied over the top surface of thecontiguous semiconductor material layer and lithographically patterned.The pattern in the photoresist is transferred into the contiguoussemiconductor material layer by the etch, which is typically ananisotropic etch. After removal of the photoresist, the trenches arefilled with a dielectric material such as a dielectric oxide, adielectric nitride, a dielectric nitride, or a combination thereof. Forexample, silicon oxide and/or silicon nitride may be deposited into thetrenches. The dielectric material above the top surface of thecontiguous semiconductor material layer is removed, for example, bychemical mechanical planarization. The remaining portions of thedielectric material filling the trenches constitute shallow trenchisolation (STI) structures 34. Pad dielectric layers (not shown) may beemployed to facilitate the planarization process.

The remaining portion of the contiguous semiconductor material layerconstitutes a top semiconductor portion, which includes a primary topsemiconductor portion 30P, first laterally protruding top semiconductorportions 30A, and second laterally protruding top semiconductor portions30B. The primary top semiconductor portion 30P, the first laterallyprotruding top semiconductor portions 30A, and the second laterallyprotruding top semiconductor portions 30B comprise the samesemiconductor material, have the same thickness, i.e., the firstthickness t1, and are epitaxially aligned among one another. Thesidewalls of the top semiconductor portion (30P, 30A, 30B) are laterallyabutted by the shallow trench isolation structures 34. The firstlaterally protruding top semiconductor portions 30A and the secondlaterally protruding top semiconductor portions 30B laterally protrudeout of the sidewalls of the primary top semiconductor portion 30P intothe shallow trench isolation structures 34. Thus, each of the firstlaterally protruding top semiconductor portions 30A and the secondlaterally protruding top semiconductor portions 30B may comprisemultiple sidewalls that laterally abut the shallow trench isolationstructures 34. The shallow trench isolation structures 34 and the topsemiconductor portion (30P, 30A, 30B) have substantially the samethickness, i.e., the first thickness t1.

At least one pair of a first laterally protruding top semiconductorportions 30A and a second laterally protruding top semiconductorportions 30B may be formed on one side of the primary top semiconductorportion 30P, and at least another pair of a first laterally protrudingtop semiconductor portions 30A and a second laterally protruding topsemiconductor portions 30B may be formed on an opposite side of theprimary top semiconductor portion 30P. The width of the semiconductorportion SPW may be from about 400 nm to about 3,000 nm, and preferablyfrom about 600 nm to about 1,500 nm, although lesser and greater widthscan also be employed. The length of the semiconductor portion SPL is thelength of a semiconductor waveguide that is intended to be manufactured,and may be from about 10 μm to about 3 cm, and typically from about 30μm to about 1 cm, although lesser and greater lengths can also beemployed. Further, configurations for a semiconductor waveguide having acurvature or a taper can also be employed, in which the shape of the topsemiconductor portion (30P, 30A, 30B) are adjusted with a curvature, ataper, and/or other suitable geometric adjustments.

Referring to FIGS. 2A-2C, a first photoresist is applied over the topsurfaces of the top semiconductor portion (30P, 30A, 30B) and theshallow trench isolation structures 34 and lithographically patterned.The pattern in the first photoresist includes a pair of line troughsseparated by a central photoresist portion 37A, which is a remainingportion of the first photoresist after lithographic patterning. Thecentral photoresist portion 37A has a constant width, which is hereinreferred to as a waveguide width ww. The waveguide width ww may be fromabout 200 nm to about 1,500 nm, and preferably from about 300 nm toabout 750 nm, although lesser and greater widths can also be employed.The remaining portions of the first photoresist include a first-sidephotoresist portion 37B and a second-side photoresist portion 37C, whichare separated from the central photoresist portion 37A by the pair ofline troughs. Each of the line troughs may have a substantially constantwidth, which is herein referred to as a line trough width ltw. The twoline troughs may have the same line trough width ltw, or may havedifferent line trough widths ltw. The sum of the two line trough widthsltw and the waveguide width ww may be less than, equal to, or greaterthan the width of the semiconductor portion SPW. While the presentinvention is described for the case in which the sum of the two linetrough widths ltw and the waveguide width ww is less than the width ofthe semiconductor portion SPW, embodiments in which the sum of the twoline trough widths ltw and the waveguide width ww is equal to, orgreater than, the width of the semiconductor portion SPW are explicitlycontemplated herein.

The pattern in the patterned portions of the first photoresist, i.e.,the set of the central photoresist portion 37A, the first-sidephotoresist portion 37B, and the second-side photoresist portion 37C istransferred into the primary top semiconductor portion 30P, for example,by an anisotropic etch such as a reactive ion etch (RIE). The exposedportions of the primary top semiconductor portion 30P are verticallyrecessed by a recess depth rd, which is less than the first thicknesst1. A pair of recessed line trenches 31 is formed directly underneaththe two line troughs between the central photoresist portion 37A andeach of the first-side and second-side photoresist portions (37B, 37C).

The recessed portions of the primary top semiconductor portion 30P areherein referred to as recessed semiconductor regions 30R. The recessedsemiconductor regions have a second thickness t2, which is equal to thedifference between the first thickness t1 and the recess depth rd. Thesecond thickness t2 may be from about 10 nm to about 200 nm, andtypically from about 30 nm to about 100 nm, although lesser and greaterthicknesses can also be employed. The remaining sub-portion of theprimary top semiconductor portion 30P underneath the central photoresistportion 37A is herein referred to a semiconductor waveguide 30. Thesemiconductor waveguide 30 has the first thickness t1 and the waveguidewidth ww. The semiconductor waveguide 30 may be employed to transmitlight along the direction of the length of the semiconductor portion SPL(See FIG. 1A). The sub-portions of the top semiconductor portion 30Pdirectly underneath the pair of line trenches 31 are the recessedsemiconductor regions 30R, which are of integral construction with thesemiconductor waveguide 30.

The first-side photoresist portion 37B and the second-side photoresistportion 37C cover the upper surfaces of the first laterally protrudingtop semiconductor portions 30A and the second laterally protruding topsemiconductor portions 30B. Thus, the first-side photoresist portion 37Band the second-side photoresist portion 37C are not recessed by theanisotropic etch, and have the first thickness t1. Each of the firstlaterally protruding top semiconductor portions 30A and the secondlaterally protruding top semiconductor portions 30B is a sup-portion ofthe top semiconductor portion (30P, 30A, 30 b) having the firstthickness t1. Sidewalls of the first laterally protruding topsemiconductor portions 30A and the second laterally protruding topsemiconductor portions 30B are exposed to the pair of recessed linetrenches 31.

The semiconductor waveguide 30, the recessed semiconductor regions 30R,the first-side photoresist portions 37B, and the second-side photoresistportions 37C are of integral and unitary construction, i.e., in a singlecontiguous structure without any interface therebetween. In case theentirety of the top semiconductor portion (30P, 30A, 30B) is singlecrystalline prior to the formation of the semiconductor waveguide 30,the semiconductor waveguide 30, the recessed semiconductor regions 30R,the first-side photoresist portions 37B, and the second-side photoresistportions 37C are single crystalline and epitaxially aligned among oneanother. In case the semiconductor substrate is an SOI substrate, thesemiconductor waveguide 30, the semiconductor waveguide 30, the recessedsemiconductor regions 30R, the first-side photoresist portion 37B, thesecond-side photoresist portion 37C, and the shallow trench isolationstructures 34 are formed in a top semiconductor layer of the SOIsubstrate.

Referring to FIGS. 3A-3F, the first photoresist is removed selective tothe semiconductor material of the semiconductor waveguide 30, therecessed semiconductor regions 30R, the first-side photoresist portion37B, the second-side photoresist portion 37C. Preferably, the removal ofthe first photoresist is selective to the dielectric material of theshallow trench isolation structures 34. While the present invention isdescribed for the case in which edges of the recessed line trenches 31is coincident with the sidewalls of the shallow trench isolationstructures 34 that laterally abut the primary top semiconductor portion30P (See FIG. 1A), embodiments in which the edges of the recessed linetrenches 31 is offset from the sidewalls of the shallow trench isolationstructures 34 inward or outward are explicitly contemplated herein.

Referring to FIGS. 4A-4C, a second photoresist 45 is applied over thefirst exemplary semiconductor structure and lithographically patternedto form openings. The first laterally protruding top semiconductorportions 30A are exposed within the openings. Further, portions of therecessed semiconductor regions 30R that adjoin the first laterallyprotruding top semiconductor portions 30A are also exposed within theopening in the second photoresist 45. The second photoresist 45 coversthe entirety of the semiconductor waveguide 30 and the second laterallyprotruding top semiconductor portions 30B. Further, the secondphotoresist 45 covers portions of the recessed semiconductor regions 30Rthat laterally abut the semiconductor waveguide 30.

P-type dopants are implanted into the first laterally protruding topsemiconductor portions 30A and the exposed portions of the recessedsemiconductor regions 30R. P-type dopants may be boron, gallium, indium,or a combination thereof. Preferably, the dose and the energy of thep-type dopants are selected to provide a heavy doping in the implantedregions. For example, the atomic concentration of p-type dopants in theimplanted regions may be from about 1.0×10¹⁹/cm³ to about 1.0×10²¹/cm³,and typically from about 5.0×10¹⁹/cm³ to about 5.0×10²⁰/cm³, althoughlesser and greater dopant concentrations can also be employed.

The first laterally protruding top semiconductor portions 30A asimplanted with the p-type dopants are herein referred to as p-dopednon-recessed semiconductor regions 46A, which has a third thickness t3.Typically, the third thickness t3 is the same as the first thickness t1.The portions of the recessed semiconductor regions 30R that areimplanted with the p-type dopants are herein referred to as p-dopedrecessed semiconductor regions 46B. A contiguous pair of a p-dopednon-recessed semiconductor region 46A and a p-doped recessedsemiconductor region 46B collectively constitutes a p-dopedsemiconductor region (46A, 46B). The portions of the recessedsemiconductor regions 30R that are not implanted with the p-type dopantsare herein referred to as substantially undoped recessed semiconductorregions 32, which has the same composition as the semiconductorwaveguide 30, i.e., has a total concentration of impurities, includingdopants, less than about 1.0×10¹⁶/cm³.

Within each p-doped semiconductor region (46A, 46B), a p-dopednon-recessed semiconductor region 46A laterally abuts a p-doped recessedsemiconductor region 46B. Further, each p-doped recessed semiconductorregion 46B laterally abuts a substantially undoped recessedsemiconductor region 32. The second photoresist 45 is subsequentlyremoved.

Referring to FIGS. 5A-5C, a third photoresist 47 is applied over thefirst exemplary semiconductor structure and lithographically patternedto form openings. The second laterally protruding top semiconductorportions 30B are exposed within the openings. Further, portions of thesubstantially undoped recessed semiconductor regions 32 that adjoin thesecond laterally protruding top semiconductor portions 30B are alsoexposed within the opening in the third photoresist 47. The thirdphotoresist 47 covers the entirety of the semiconductor waveguide 30 andthe p-doped semiconductor region (46A, 46B). Further, the thirdphotoresist 47 covers portions of the substantially undoped recessedsemiconductor regions 32 that laterally abut the semiconductor waveguide30.

N-type dopants are implanted into the second laterally protruding topsemiconductor portions 30B and the exposed portions of the substantiallyundoped recessed semiconductor regions 32. N-type dopants may bephosphorus, arsenic, antimony, or a combination thereof. Preferably, thedose and the energy of the n-type dopants are selected to provide aheavy doping in the implanted regions. For example, the atomicconcentration of n-type dopants in the implanted regions may be fromabout 1.0×10¹⁹/cm³ to about 1.0×10²¹/cm³, and typically from about5.0×10¹⁹/cm³ to about 5.0×10²⁰/cm³, although lesser and greater dopantconcentrations can also be employed.

The second laterally protruding top semiconductor portions 30B asimplanted with the n-type dopants are herein referred to as n-dopednon-recessed semiconductor regions 48A, which has the third thicknesst3. The portions of the substantially undoped recessed semiconductorregions 32 that are implanted with the n-type dopants are hereinreferred to as n-doped recessed semiconductor regions 48B. A contiguouspair of an n-doped non-recessed semiconductor region 48A and an n-dopedrecessed semiconductor region 48B collectively constitutes an n-dopedsemiconductor region (48A, 48B). The substantially undoped recessedsemiconductor regions 32 is reduced as portions of the substantiallyundoped recessed semiconductor regions 32 are converted into the n-dopedrecessed semiconductor regions 48B.

Within each n-doped semiconductor region (48A, 48B), an n-dopednon-recessed semiconductor region 48A laterally abuts an n-dopedrecessed semiconductor region 48B. Further, each n-doped recessedsemiconductor region 48B laterally abuts a substantially undopedrecessed semiconductor region 32. The third photoresist 47 issubsequently removed.

Referring to FIGS. 6A-6C, the first exemplary semiconductor structureafter removal of the third photoresist 47 is shown. The substantiallyundoped recessed semiconductor regions 32, the p-doped recessedsemiconductor regions 46B, and the n-doped recessed semiconductorregions 48B collectively constitute the recessed semiconductor regions(32, 46B, 48B). The recessed semiconductor regions (32, 46B, 48B)underlie the pair of recessed line trenches 31. The p-doped non-recessedsemiconductor regions 48A, the n-doped non-recessed semiconductorregions 48A, and the semiconductor waveguide 30 are not recessed. Eachof the p-doped non-recessed semiconductor regions 48A and the n-dopednon-recessed semiconductor regions 48A has a sidewall that is exposed toone of the recessed line trenches 31. The semiconductor waveguide 30 hastwo substantially parallel and substantially vertical sidewallsseparated by the waveguide width ww. Each sidewall of the semiconductorwaveguide 30 is exposed to one of the two recessed line trenches 31.

Referring to FIGS. 7A-7C, a dielectric layer 60L is formed directly onthe exposed surfaces of the first exemplary semiconductor structureincluding the top surface and the sidewall surfaces of the semiconductorwaveguide 30, the top surfaces of the recessed semiconductor regions(32, 46B, 48B), the top surfaces and the sidewalls of the p-dopednon-recessed semiconductor region 46A and the n-doped non-recessedsemiconductor region 48A, and the top surfaces of the shallow trenchisolation structures 34. The dielectric layer 60L comprises a dielectricmaterial such as a dielectric oxide, a dielectric nitride, a dielectricoxynitride, or a combination thereof. For example, the dielectric layer60L may comprise silicon nitride or silicon oxide. The dielectricmaterial for the dielectric layer 60L has a lower refractive index thanthe semiconductor material of the semiconductor waveguide 30.

The dielectric layer 60L may be conformal or non-conformal. Thethickness of the dielectric layer 60L, as measured on the top surface ofthe semiconductor waveguide 30, may be from about 4 nm to about 100 nm,and typically from about 10 nm to about 50 nm, although lesser andgreater thicknesses can also be employed. The dielectric layer 60L maybe formed by low pressure chemical vapor deposition (LPCVD), plasmaenhanced chemical vapor deposition (PECVD), rapid thermal chemical vapordeposition (RTCVD), atomic layer deposition (ALD), etc.

Referring to FIGS. 8A-8C, the dielectric layer 60L is lithographicallypatterned into at least three portions. The lithographic patterning maybe effected by applying a photoresist (not shown) to the top surface ofthe dielectric layer 60L and lithographically patterning thephotoresist, followed by a pattern transfer into the dielectric layer byan etch. The etch may be an anisotropic etch or an isotropic etch.

Remaining portions of the dielectric layer 60L after the lithographicpatterning include a dielectric material portion 62 which covers theentirety of the top surface and sidewalls of the semiconductor waveguide30. The remaining portions of the dielectric layer 60L further includesdielectric spacers 64, each of which is located directly on at least oneof a sidewall of a p-doped non-recessed semiconductor region 46A and asidewall of an n-doped non-recessed semiconductor region 48A. In oneembodiment, a dielectric spacer 64 may be formed contiguously anddirectly on a sidewall of a p-doped non-recessed semiconductor region46A, a sidewall of an n-doped non-recessed semiconductor region 48A, anda sidewall of one of the shallow trench isolation structures 34 that islocated between the p-doped non-recessed semiconductor region 46A andthe sidewall of an n-doped non-recessed semiconductor region 48A.Horizontal surfaces of the p-doped non-recessed semiconductor regions46A, the n-doped non-recessed semiconductor regions 48A, the p-dopedrecessed semiconductor regions 46B, and the n-doped recessedsemiconductor regions 48B are exposed. All sidewalls of the p-dopednon-recessed semiconductor regions 46A and the n-doped non-recessedsemiconductor regions 48A are covered by the dielectric spacers 64.

On each side of the semiconductor waveguide 30, a contiguous set ofexposed semiconductor surfaces is formed, which includes a top surfaceof a p-doped recessed semiconductor regions 46B, a top surface of ann-doped recessed semiconductor regions 48B, and a top surface of aportion of a substantially undoped recessed semiconductor regions 32located therebetween.

Referring to FIGS. 9A-9C, various metal semiconductor alloy portions areformed on the exposed semiconductor surfaces of the first exemplarysemiconductor structure. Specifically, recessed metal semiconductoralloy portions 72 are formed directly on the exposed surfaces of therecessed semiconductor regions (32, 46B, 48B). First metal semiconductoralloy portions 66 are formed directly on the top surfaces of the p-dopednon-recessed semiconductor regions 46A. Second metal semiconductor alloyportions 68 are formed directly on the top surfaces of the n-dopednon-recessed semiconductor regions 46B.

The various metal semiconductor alloy portions (72, 66, 68) may beformed by methods known in the art such as deposition of a blanket metallayer, anneal at an elevated temperature to induce formation of metalsemiconductor alloy materials, and removal of unreacted portions of theblanket metal layer. In case the semiconductor material of the recessedsemiconductor regions (32, 46B, 48B) and the doped non-recessedsemiconductor regions (46A, 48A) comprise silicon, the various metalsemiconductor alloy portions (72, 66, 68) comprise a metal silicide. Incase the semiconductor material of the recessed semiconductor regions(32, 46B, 48B) and the doped non-recessed semiconductor regions (46A,48A) comprise germanium, the various metal semiconductor alloy portions(72, 66, 68) comprise a metal germanide. The recessed metalsemiconductor alloy portions 72, the first metal semiconductor alloyportions 66, and the second metal semiconductor alloy portions 68comprise the same metal semiconductor alloy material.

A middle-of-line (MOL) dielectric material layer 80 is formed on thefirst exemplary semiconductor structure. The pair of line troughs 31 isfilled with the MOL dielectric layer 80. The dielectric materials thatmay be used for the MOL dielectric layer 80 include, but are not limitedto, a silicate glass, an organosilicate glass (OSG) material, aSiCOH-based low-k material formed by chemical vapor deposition, aspin-on glass (SOG), or a spin-on low-k dielectric material such asSiLK™, etc. The silicate glass includes an undoped silicate glass (USG),borosilicate glass (BSG), phosphosilicate glass (PSG), fluorosilicateglass (FSG), borophosphosilicate glass (BPSG), etc. The dielectricmaterial may be a low dielectric constant (low-k) material having adielectric constant less than 3.0. The dielectric material maynon-porous or porous.

A conductive contact via is formed directly on each of the first metalsemiconductor alloy portions 66 and the second metal semiconductor alloyportions 68. Specifically, a first conductive contact via 86 is formeddirectly on each of the first metal semiconductor alloy portion 66, anda second conductive contact via 88 is formed directly on each of thesecond metal semiconductor alloy portion 68. The first and second metalsemiconductor alloy portions (66, 68) comprise a conductive materialsuch as doped polysilicon, a doped silicon-containing semiconductormaterial, W, Cu, Al, TaN, TiN, Ta, Ti, or a combination thereof.

Heat may be transferred between the semiconductor waveguide 30 and theset of the first metal semiconductor alloy portions 66 and the secondmetal semiconductor alloy portions 68 by passing current. Specifically,a voltage bias may be applied across a resistively connected pair of afirst conducive contact via 86 and a second conductive contact via 88.

In one embodiment, the second conductive contact via 88 is held at apositive voltage relative to the first conductive contact via 86. Inthis case, electrical current flows from the second conductive contactvia 88, then through a second metal semiconductor alloy portion 68, thenthrough an n-doped non-recessed semiconductor region 48A, then throughan n-doped recessed semiconductor region 48B, then through a recessedmetal semiconductor alloy portion 72, then through a p-doped recessedsemiconductor region 46B, then through a p-doped non-recessedsemiconductor region 46A, then through a first metal semiconductor alloyportion 66, and into the first conductive contact via 86. In metallicmaterials or metal semiconductor alloy portions in the current path,electrons move in the opposite direction of the current flow to conductelectricity.

In semiconductor material portions, majority charge carriers provideelectrical conduction. Specifically, holes having positive chargestravel in the p-doped recessed semiconductor region 46B and the p-dopednon-recessed semiconductor region 46A along the direction from therecessed metal semiconductor alloy portion 72 toward the first metalsemiconductor alloy portion 66. Electrons having negative charges travelin the n-doped recessed semiconductor region 48B and the n-dopednon-recessed semiconductor region 48A along the direction from therecessed metal semiconductor alloy portion 72 toward the second metalsemiconductor alloy portion 68. Thus, the majority charge carrierstravel away from the recessed metal semiconductor alloy portion 72 inthe p-doped semiconductor region (46A, 46B) and the n-dopedsemiconductor region (48A, 48B).

The mechanism of Peltier-Seebeck effect is in operation in the p-dopedsemiconductor region (46A, 46B) and the n-doped semiconductor region(48A, 48B). According to Peltier-Seebeck effect, heat transferaccompanies diffusion of charge carriers in a semiconductor material andvice versa. In this case, the majority charge carriers diffuse away fromthe interface with the recessed metal semiconductor alloy portion 72toward the interface with the first or second metal semiconductor alloyportion (66 or 68) in each of the p-doped semiconductor region (46A,46B) and the n-doped semiconductor region (48A, 48B). Therefore, thereis a net heat transfer from the recessed metal semiconductor alloyportion 72 to the first and second metal semiconductor alloy portions(66, 68). The heat that is transferred to the first and second metalsemiconductor alloy portions (66, 68) may further be transferred to aheat sink through the first and second conductive contact vias (86, 88)and other metal interconnect structures (not shown) attached thereto.

Since the semiconductor waveguide 30, the recessed semiconductor regions(32, 46B, 48B), the p-doped semiconductor region (46A, 46B), and then-doped semiconductor region (48A, 48B) are of integral constructionwithout any interface therebetween, the entirety of the semiconductorwaveguide 30, the recessed semiconductor regions (32, 46B, 48B), thep-doped semiconductor region (46A, 46B), and the n-doped semiconductorregion (48A, 48B) is thermally connected among one another. Continualtransfer of heat from the recessed metal semiconductor alloy portions72, through the p-doped semiconductor region (46A, 46B) and the n-dopedsemiconductor region (48A, 48B), and into the first and second metalsemiconductor alloy portions (66, 68) cools the semiconductor waveguide30.

Cooling of the semiconductor waveguide 30 affects the refractive indexof the semiconductor material of the semiconductor waveguide. Forexample, single crystalline silicon has a wavelength-dependentrefractive index, which is from about 3.42 to about 3.56 between thewavelength range from about 1 micron to about 6 microns. The temperaturedependency of the refractive index of silicon is about 1.6×10⁻⁴ perdegree Celsius. Germanium has similar temperature dependency as silicon.

Temperature change in the semiconductor waveguide 30 may beadvantageously employed to change the phase of light passing through thesemiconductor waveguide. For example, light having a wavelength of about3.42 micron in vacuum has a wavelength of about 1.00 micron in asemiconductor waveguide 30 that consists essentially of silicon. 1degree change in the temperature of the semiconductor waveguide 30induces a phase change of about 2π×1.6×10⁻⁴ radian per 1 micron. Thelight changes phase by π radian after traveling about 3.125 mm. Byemploying a beam splitter connected to two semiconductor waveguides 30and modulating the phase of the light in one of the semiconductorwaveguides 30, constructive interference or destructive interference maybe induced between the two beams as the phase of one beam is modulatedthrough cooling. Thus, by modulating the refractive index of asemiconductor waveguide 30 through the temperature change in thesemiconductor waveguide 30 caused by heat transfer out of thesemiconductor waveguide 30, the phase of the light passing through thesemiconductor waveguide 30 may be modulated.

In another embodiment, the second conductive contact via 88 is held at anegative voltage relative to the first conductive contact via 86. Inthis case, electrical current flows from the first conductive contactvia 86, then through a first metal semiconductor alloy portion 66, thenthrough a p-doped non-recessed semiconductor region 46A, then through ap-doped recessed semiconductor region 46B, then through a recessed metalsemiconductor alloy portion 72, then through an n-doped recessedsemiconductor region 48B, then through an n-doped non-recessedsemiconductor region 48A, then through a second metal semiconductoralloy portion 68, and into the second conductive contact via 88. Inother words, the electrical current flows in the opposite direction ofthe current flow in the previous embodiment.

In this case, holes in the p-doped semiconductor region (46A, 46B) alongthe direction from the first metal semiconductor alloy portion 66 to therecessed metal semiconductor alloy portion 72. Electrons travel in then-doped semiconductor region (48A, 48B) along the direction from thesecond metal semiconductor alloy portion 68 toward the recessed metalsemiconductor alloy portion 72. Thus, the majority charge carrierstravel toward the recessed metal semiconductor alloy portion 72 in thep-doped semiconductor region (46A, 46B) and the n-doped semiconductorregion (48A, 48B).

The mechanism of Peltier-Seebeck effect is also in operation in thep-doped semiconductor region (46A, 46B) and the n-doped semiconductorregion (48A, 48B). However, the majority charge carriers diffuse awayfrom the interface with the first or second metal semiconductor alloyportion (66 or 68) toward the interface with the recessed metalsemiconductor alloy portion 72 in each of the p-doped semiconductorregion (46A, 46B) and the n-doped semiconductor region (48A, 48B).Therefore, there is a net heat transfer from the first and second metalsemiconductor alloy portions (66, 68) to the recessed metalsemiconductor alloy portion 72.

Since the entirety of the semiconductor waveguide 30, the recessedsemiconductor regions (32, 46B, 48B), the p-doped semiconductor region(46A, 46B), and the n-doped semiconductor region (48A, 48B) is thermallyconnected among one another, heat transferred into the recessed metalsemiconductor alloy portion 72 is transferred into the semiconductorwaveguide 30. Thus, the semiconductor waveguide is heated as the currentflows through the p-doped semiconductor region (46A, 46B) and then-doped semiconductor region (48A, 48B). The mechanism for the heataccumulation in the semiconductor waveguide 30 is not Joule heating, buta heat transfer through Peltier-Seebeck effect.

Heating of the semiconductor waveguide 30 affects the refractive indexof the semiconductor material of the semiconductor waveguide in the samemanner as the cooling of the semiconductor waveguide 30 except for thereversal of the polarity of the change in the refractive index. In asimilar manner as in the previous embodiment, temperature change in thesemiconductor waveguide 30 may be advantageously employed to change thephase of light passing through the semiconductor waveguide. Bymodulating the refractive index of a semiconductor waveguide 30 throughthe temperature change in the semiconductor waveguide 30 caused by heattransfer into the semiconductor waveguide 30, the phase of the lightpassing through the semiconductor waveguide 30 may be modulated.

Referring to FIG. 10, a second exemplary semiconductor structureaccording to a second embodiment of the present invention comprises asemiconductor substrate 108, which is a semiconductor-on-insulator (SOI)substrate. The SOI substrate includes a handle substrate 10, aninsulator layer 20 abutting a top surface of the handle substrate 10,and a top semiconductor layer 129 located above the insulator layer 20.The insulator layer 20 and the handle substrate 10 provide structuralsupport to the top semiconductor layer 129 which may comprise acontiguous semiconductor material layer that covers the entirety of theinsulator layer 20. The top semiconductor layer 129 comprises asemiconductor material, which may be any of the material that may beemployed for the contiguous semiconductor material layer of the firstembodiment.

Preferably, the top semiconductor layer 129 comprises a substantiallyundoped semiconductor material so that the amount of impurities,including dopant atoms, in the top semiconductor layer 129 is minimized.By minimizing the amount of impurities in the contiguous material layer,a semiconductor waveguide having a low absorption rate of the signal maybe subsequently formed from a portion of the top semiconductor layer.The atomic concentration of impurities, including dopants, in the topsemiconductor layer 129 is less than about 1.0×10¹⁶/cm³, and preferablyless than about 1.0×10¹⁵/cm³, and more preferably less than about1.0×10¹⁴/cm³. In case the top semiconductor layer 129 comprises silicon,the resistivity of the material of the top semiconductor layer 129 isgreater than about 1 Ohm-cm, and preferably greater than about 10Ohm-cm, and more preferably greater than about 100 Ohm-cm.

The buried insulator layer 20 comprises a dielectric material such as adielectric oxide, a dielectric nitride, or a dielectric oxynitride. Forexample, the buried insulator layer 20 may comprise silicon oxide. Theburied insulator layer 20 may comprise a dielectric material having adielectric constant greater than 3.0.

The handle substrate 10 may comprise a semiconductor material, aninsulator material, a conductive material, or a combination thereof. Incase the handle substrate 10 comprises a semiconductor material, thematerial for the handle substrate 10 may comprise any of thesemiconductor material that may be employed for the top semiconductorlayer 129 as described above.

Referring to FIG. 11, a hard mask layer 125 may be deposited on a topsurface of the top semiconductor layer 129 and lithographicallypatterned to mask a portion of the top semiconductor layer 129, whileexposing other portions of the top semiconductor layer 129. The hardmask layer 125 comprises a dielectric material such as silicon oxide,silicon nitride, or silicon oxynitride. The exposed portions of the topsemiconductor layer 129 are recessed. An epitaxial semiconductor layer127 may be deposited on the recessed surface of the top semiconductorlayer 129. The epitaxial semiconductor layer may comprise a differentsemiconductor material than the top semiconductor layer 129. Thematerial of the epitaxial semiconductor layer 127 is single crystalline,and is epitaxially aligned to semiconductor material of the topsemiconductor layer 127. For example, the top semiconductor layer 129may comprise single crystalline silicon, and the epitaxial semiconductorlayer 127 may comprise a silicon germanium alloy.

The hard mask layer 125 is subsequently removed. The top surface of thetop semiconductor portions of the top semiconductor layer 129 may beplanarized, for example, by chemical mechanical planarization.

Referring to FIGS. 12A and 12B, portions of the top semiconductor layer129 are appropriately doped and patterned to form at least one p-dopedsemiconductor portion (131, 132) and at least one n-doped semiconductorportion (133, 134). Each of the at least one p-doped semiconductorregion (131, 132) may comprise a lower p-doped semiconductor region 131and an upper p-doped semiconductor region 132. Each of the at least onen-doped semiconductor region (133, 134) may comprise a lower n-dopedsemiconductor region 133 and an upper n-doped semiconductor region 134.In addition, a semiconductor waveguide 136 may be formed by a patterninganother portion of the top semiconductor layer 129 without implantingadditional dopant atoms. In this case, the semiconductor waveguide maycomprise a substantially intrinsic semiconductor material having thesame composition as the at least one p-doped semiconductor portion (131,132) and the at least one n-doped semiconductor portion (133, 134)except for dopant species and dopant concentration. The substantiallyintrinsic semiconductor material may have a resistivity greater than 1Ohm-cm as the material of the top semiconductor layer 129 describedabove. In one case, the semiconductor waveguide 136 may consistessentially of silicon, and the at least one lower p-doped semiconductorregion 131 may consist essentially of p-doped silicon, and the at leastone n-doped semiconductor region 133 may consist essentially of n-dopedsilicon.

The at least one upper p-doped semiconductor portion 132 may be formedby implanting p-type dopants into at least one portion of the epitaxialsemiconductor layer 127 through at least one opening in a firstimplantation mask layer (not shown), which may be a first patternedphotoresist layer. The at least one lower p-doped semiconductor portion131 may be formed by implanting p-type dopants into at least one portionof the top semiconductor layer 129 through the at least one opening inthe first implantation mask layer. The at least one upper n-dopedsemiconductor portion 134 may be formed by implanting n-type dopantsinto at least one portion of the epitaxial semiconductor layer 127through at least one opening in a second implantation mask layer (notshown), which may be a second patterned photoresist layer. The at leastone lower n-doped semiconductor portion 133 may be formed by implantingn-type dopants into at least one portion of the top semiconductor layer129 through the at least one opening in the second implantation masklayer.

After implantation of the p-type dopants and the n-type dopants, the topsemiconductor layer 129 is lithographically patterned. The remainingportions of the epitaxial semiconductor layer 127 and the topsemiconductor layer 129 after lithographic patterning include the atleast one p-doped semiconductor portion (131, 132), the at least onen-doped semiconductor portion (133, 134), and optionally, thesemiconductor waveguide 136. Thus, the heights of the at least onep-doped semiconductor portion (131, 132), the at least one n-dopedsemiconductor portion (133, 134), and the semiconductor waveguide 136are substantially the same at this step.

Each of the at least one p-doped semiconductor portion (131, 132) maylaterally abut the at least one n-doped semiconductor portion (133,134). Alternately, a substantially undoped semiconductor materialportion (not shown) having the same composition as the semiconductorwaveguide 136 may be formed between one of the at least one p-dopedsemiconductor portion (131, 132) and the at least one n-dopedsemiconductor portion (133, 134).

Referring to FIGS. 13A and 13B, metal semiconductor alloy regions areformed on the sub-portions of the at least one upper p-dopedsemiconductor portion 132 and the at least one upper n-dopedsemiconductor portion 134. Specifically, a first metal semiconductoralloy region 140 is formed on each laterally abutting pair of a firstsub-portion of the at least one p-doped semiconductor portion (131, 132)and a first sub-portion of the at least one n-doped semiconductorportion (133, 134). Each first metal semiconductor alloy region 140 iscontiguous.

A second metal semiconductor alloy region 142 is formed on a secondsub-portion of each of the at least one upper p-doped semiconductorportion 132. The second sub-portion of each of the at least one upperp-doped semiconductor portion 132 is located on an opposite end of thefirst sub-portion of that p-doped semiconductor portion 134. In each ofthe at least one p-doped semiconductor portion (131, 132), a middlesub-portion of the p-doped semiconductor portion (131, 132) that doesnot underlie a metal semiconductor alloy region separates, and laterallyabuts, a first sub-portion of the p-doped semiconductor portion (131,132) and a second sub-portion of the p-doped semiconductor portion (131,132). Each of the at least one p-doped semiconductor portion (131, 132)includes a first sub-portion located directly underneath a portion of afirst metal semiconductor alloy region 140, a second sub-portion locateddirectly underneath a second metal semiconductor alloy region 142, and amiddle sub-portion that laterally separates the first sub-portion andthe second sub-portion of that p-doped semiconductor portion (131, 132).

A third metal semiconductor alloy region 144 is formed on a secondsub-portion of each of the at least one upper n-doped semiconductorportion 134. The second sub-portion of each of the at least one uppern-doped semiconductor portion 134 is located on an opposite end of thefirst sub-portion of that n-doped semiconductor portion (133, 134). Ineach of the at least one n-doped semiconductor portion (133, 134), amiddle sub-portion of the n-doped semiconductor portion (133, 134) thatdoes not underlie a metal semiconductor alloy region separates, andlaterally abuts, a first sub-portion of the n-doped semiconductorportion (133, 134) and a second sub-portion of the n-doped semiconductorportion (133, 134). Each of the at least one n-doped semiconductorportion (133, 134) includes a first sub-portion located directlyunderneath a portion of a first metal semiconductor alloy region 140, asecond sub-portion located directly underneath a third metalsemiconductor alloy region 144, and a middle sub-portion that laterallyseparates the first sub-portion and the second sub-portion of thatp-doped semiconductor portion (131, 132).

The metal semiconductor alloy regions (140, 142, 144) may be formed bydepositing an insulator layer (not shown), patterning openings in theinsulator layer in areas in which the metal semiconductor alloy regions(140, 142, 144) are to be formed, depositing a metal layer, reacting thematerial of the metal layer with the underlying semiconductor material,and removing unreacted portions of the metal layer. The insulator layermay, or may not, be subsequently removed. The metal layer comprises ametal that reacts with the underlying semiconductor material of the atleast one p-doped semiconductor portion (131, 132) and the at least onen-doped semiconductor portion (133, 134). Non-limiting examples of themetal that may be employed as the material of the metal layer includeCo, Ta, Ti, W, Ni, Pt, Os, and Ir. In case the underlying semiconductormaterial comprises silicon, the metal semiconductor alloy regions (140,142, 144) may comprise a metal silicide. The thickness of the metalsemiconductor alloy regions (140, 142, 144) may be from 10 nm to 100 nm,although lesser and greater thicknesses can also be employed.

Referring to FIGS. 14A and 14B, a photoresist 147 is applied over thetop surface of the second exemplary semiconductor structure. An openingis formed in the photoresist 147 by lithographic patterning. The atleast one first metal semiconductor alloy region 140 is exposed withinthe opening in the photoresist 147. A portion of the semiconductorwaveguide 136 may be exposed within the opening in the photoresist 147.Not necessarily but preferably, edges of the photoresist 147 may overliethe middle sub-portion(s) of the at least one p-doped semiconductorportion (131, 132) and the middle sub-portion(s) of the at least onen-doped semiconductor portion (133, 134).

Portions of the top surface of the buried insulator layer 20 are exposedwithin the opening in the photoresist 147. The exposed portions of theburied insulator layer 20 are removed from underneath the opening in thephotoresist 147 by an etch, which may be an isotropic etch or ananisotropic etch. The photoresist 147 protects covered portions of theburied insulator layer 20 from the etch. The etch is selective to themetal semiconductor alloy portions (140, 142, 144), the at least onep-doped semiconductor portion (131, 132), the at least one n-dopedsemiconductor portion (133, 134), and the semiconductor waveguide 136. Atrench is formed within the buried insulator layer 20 underneath theopening in the photoresist 147. A top surface of the handle substrate 10may be exposed underneath the trench in the buried insulator layer 20.

The trench may undercut the at least one p-doped semiconductor portion(131, 132), the at least one n-doped semiconductor portion (133, 134),and a portion of the semiconductor waveguide 136. Preferably, theundercut of the at least one p-doped semiconductor portion (131, 132),the at least one n-doped semiconductor portion (133, 134), and a portionof the semiconductor waveguide 136 is controlled to prevent a completedissociation from the top surface of the buried insulator layer 20 andto insure that each of the at least one p-doped semiconductor portion(131, 132), the at least one n-doped semiconductor portion (133, 134),and a portion of the semiconductor waveguide 136 remains attached to theburied insulator layer 20. Preferably, the edge of the trench in theburied insulator layer 20 is directly adjoined to the middlesub-portion(s) of the at least one p-doped semiconductor portion (131,132) and the middle sub-portion(s) of the at least one n-dopedsemiconductor portion (133, 134). Each of the first sub-portion of theat least one p-doped semiconductor portion (131, 132) and each of thefirst sub-portion of the at least one n-doped semiconductor portion(133, 134) may laterally protrude from the edges of the trench withinthe buried insulator layer 20, and overhang above the trench in theburied insulator layer 20. The remaining portions of the buriedinsulator layer 20 constitute at least one dielectric material portionthat vertically abuts the bottom surfaces of the second sub-portion(s)of the at least one p-doped semiconductor portion (131, 132) and thesecond sub-portion(s) of the at leas one n-doped semiconductor portion(133, 134).

Referring to FIGS. 15A and 15B, the trench in the buried insulator layer20 is filled with a dielectric material. Preferably, the dielectricmaterial filling the trench in the buried insulator layer 20 comprises adifferent material than the dielectric material of the buried insulatorlayer 20. Preferably, the dielectric material filling the trenchcomprises a low dielectric constant (low-k) material having a dielectricconstant less than 3.0. In this case, the dielectric material fillingthe trench constitutes a low dielectric constant (low-k) dielectricmaterial portion 150. The low-k dielectric material portion 150laterally abuts the buried insulator layer 20 and vertically abuts thebottom surfaces of the first sub-portion(s) of the at least one p-dopedsemiconductor portion (131, 132) and the first sub-portion(s) of the atleas one n-doped semiconductor portion (133, 134). The interface betweenthe buried insulator layer 20 and the low-k dielectric material portion150 may be located underneath the middle sub-portion(s) of the at leastone p-doped semiconductor portion (131, 132) and the middlesub-portion(s) of the at least one n-doped semiconductor portion (133,134).

The dielectric material portion of the buried insulator layer 20comprises a dielectric material having a second edge underlying themiddle sub-portion(s) of the at least one p-doped semiconductor portion(131, 132) located between one of the at least one first metalsemiconductor region 140 and one of the at least one second metalsemiconductor region 142 and having a third edge underlying a middlesub-portion(s) of the at least one n-doped semiconductor portion (133,134) located between one of the at least one first metal semiconductorregion 140 and the at least one third metal semiconductor region 144.Further, the low-k dielectric material portion 150 comprises adielectric material having a second edge underlying the middlesub-portion(s) of the at least one p-doped semiconductor portion (131,132) located between one of the at least one first metal semiconductorregion 140 and one of the at least one second metal semiconductor region142 and having a third edge underlying a middle sub-portion(s) of the atleast one n-doped semiconductor portion (133, 134) located between oneof the at least one first metal semiconductor region 140 and the atleast one third metal semiconductor region 144.

Exemplary low-k dielectric materials that may be employed for the low-kdielectric material portion 150 include, but are not limited to,fluorinated or non-fluorinated organic polymer based low k materialssuch as Dow Chemical's SiLK™ dielectric, Honeywell's Flare™, polyimides,benzocyclobutene, polybenzoxazoles, aromatic thermoset polymers based onpolyphenylene ethers, chemical vapor deposited polymers such aspoly(p-xylylene), and organosilicate glasses (OSG's) that may bedeposited by chemical vapor deposition. Organosilicate glasses contain amatrix of a hydrogenated oxidized silicon carbon material (SiCOH)comprising atoms of Si, C, O and H in a covalently bondedtri-dimensional network, and may be referred to as SiCOH dielectricmaterials. The low-k dielectric materials may be porous or non-porous.Typically, the low-k dielectric material of the low-k dielectricmaterial portion 150 has less thermal conductivity than the dielectricmaterial of the buried insulator layer 20. The low-k dielectric materialportion 150 as deposited may cover the entirety of the second exemplarysemiconductor structure. Preferably, the top surface of the low-kdielectric material portion 150 is planar, which may be effected bydepositing a self-planarizing low-k dielectric material or byplanarizing a non-self-planarizing low-k dielectric material layer bychemical mechanical planarization, a recess etch, or a combinationthereof.

An optoelectronic device 160 is formed on the top surface of the low-kdielectric material portion 150. The optoelectronic device may be anydevice that manipulates an optical signal, i.e., electromagneticradiation. The optical signal may be in the ultraviolet range, in thevisible spectrum, in the infrared range, or in a microwave range. Theoptoelectronic device 160 may include a plurality of devices thatmanipulate at least one optical signal and may, or may not, beinterconnected amongst one another. The optoelectronic device 160 may,or may not, be optically coupled to the semiconductor waveguide 136. Incase the optoelectronic device 160 is optically coupled to thesemiconductor waveguide 136, the optoelectronic device 160 maymanipulate the optical signal that are fed into, or received from, thesemiconductor waveguide 136. The optoelectronic device 160 may includeat least one of a laser, optical amplifier, an optical sensor, awaveguide, a quantum well, or any other device that may manipulate anoptical signal. The optoelectronic device 160 may comprise anysemiconductor material that may be employed for the top semiconductorlayer 129 as described above. Particularly, the optoelectronic device160 may comprise a III-V compound semiconductor material such as GaAs,In_(x)Ga_(1-x)As, Al_(x)In_(y)Ga_(1-x-y)As, InP,In_(x)Ga_(1-x)As_(y)P_(1-y), etc. The range of x, y, and 1-x-y arebetween 0 and 1. The optoelectronic device 160 may comprise a dopedsemiconductor material or an undoped semiconductor material.

Optionally, the region of the low-k dielectric material portion 150 thatis not covered by the optoelectronic device 160 may be etched by an etchthat is selective to the optoelectronic device, the second and thirdmetal semiconductor alloy regions (142, 144), the at least one p-dopedsemiconductor portion (131, 132), and the at least one n-dopedsemiconductor portion (133, 134).

Referring to FIGS. 16A and 16B, an interconnect-level dielectricmaterial layer 80 is formed over the optoelectronic device 160 and theexposed portions of the buried insulator layer 20, the at least onesecond metal semiconductor alloy region 142, the at least one thirdmetal semiconductor alloy region 144, the at least one p-dopedsemiconductor portion (131, 132), and the at least one n-dopedsemiconductor portion (133, 134). FIG. 16A is a vertical cross-sectionalview along the vertical plane Z-Z′ in FIG. 16B, and FIG. 16B is atop-down view of selected elements including the at least one p-dopedsemiconductor portion (131, 132), the at least one first metalsemiconductor alloy region 140, the at least one second metalsemiconductor alloy region 142, the at least one third metalsemiconductor alloy region 144, and the semiconductor waveguide 136. Thelocation of the optoelectronic device 160 is shown in a broken line. Theinterconnect-level dielectric material layer 80 comprises a dielectricmaterial, which may comprise any of the dielectric material that may beemployed for the buried insulator layer or the low-k dielectric materialportion 150. Additionally or alternately, the interconnect-leveldielectric material layer 80 may comprise a doped silicate glass such asphosphosilicate glass (PSG), borosilicate glass (BSG),borophosphosilicate glass (BPSG), fluorosilicate glass (FSG), etc. Theinterconnect-level dielectric material layer 80 may further includeother dielectric materials as well.

A first set of via holes may be formed in the interconnect-leveldielectric material layer 80 above the optoelectronic device 160 andfilled with a compound semiconductor material to form at least onecompound semiconductor via 85. Each of the at least one compoundsemiconductor via vertically abuts the optoelectronic device 160 andprovides conduction of electrical current or transmission of light to orfrom the optoelectronic device 160.

A second set of via holes is formed in the interconnect-level dielectricmaterial layer 80 above each of the at least one second metalsemiconductor alloy region 142 and the at least one third metalsemiconductor alloy region 144. At least one first metal contact via 90abutting each of the at least one second metal semiconductor alloyregion 142 and at least one second metal contact via 92 abutting each ofthe at least one third metal semiconductor alloy region 144 are formedwithin the second set of via holes by filling the second set of viaholes with a conductive metal and removing excess metal from above thetop surface of the interconnect-level dielectric material layer 80. Theat least one first metal contact via 90 and the at least one secondmetal contact via 92 comprises a metallic material such as W, Ta, Ti,WN, TaN, TiN, Cu, and Al. Other metallic materials may also be employedinstead of, or in addition to, the metallic material described above.

Each adjoined set of a first metal contact via 90, a second metalsemiconductor alloy region 142, a p-doped semiconductor portion (131,132), a first metal semiconductor alloy region 140, an n-dopedsemiconductor portion (133, 134), a third metal semiconductor alloyregion 144, and a second metal contact via 92 constitutes a temperaturecontrol device (90, 142, 131, 132, 140, 133, 134, 144, 92). Eachtemperature control device (90, 142, 131, 132, 140, 133, 134, 144, 92)is configured to provide a path for conduction of electrical current.

The path for conduction of electrical current may be from a second metalcontact via 92, then through a third metal semiconductor alloy region144, then through an n-doped semiconductor portion (133, 134), thenthrough a first metal semiconductor alloy region 140, then through ap-doped semiconductor portion (131, 132), then through a second metalsemiconductor alloy region 142, and then to a first metal contact via90. This direction of current flow is herein referred to as a forwardcurrent direction. Alternately, the path for conduction of electricalcurrent may be from a first metal contact via 90, then through a secondmetal semiconductor alloy region 142, then through a p-dopedsemiconductor portion (131, 132), then through a first metalsemiconductor alloy region 140, then through an n-doped semiconductorportion (133, 134), then through a third metal semiconductor alloyregion 144, and then to a second metal contact via 92. This direction ofcurrent flow is herein referred to as a reverse current direction.

Each temperature control device (90, 142, 131, 132, 140, 133, 134, 144,92) is thermally coupled to the optoelectronic device 160, whichcomprises a semiconductor material and is configured to manipulateelectromagnetic radiation, i.e., an optical signal.

As electrical current flows through each of the at least one temperaturecontrol device (90, 142, 131, 132, 140, 133, 134, 144, 92), heat istransferred in the direction of the flow of the majority charge carrier.This is because the mechanism of Peltier-Seebeck effect is in operationin the at least one p-doped semiconductor portion (131, 132) and the atleast one n-doped semiconductor portion (133, 134). According toPeltier-Seebeck effect, heat transfer accompanies diffusion of chargecarriers in a semiconductor material and vice versa.

If the electrical current flows in the forward current direction, themajority charge carriers diffuse away from the interface with one of theat least one first metal semiconductor alloy region 140 and toward theinterface with one of the at least one second metal semiconductor alloyregion 142 and the at least one third metal semiconductor alloy region144 within the p-doped semiconductor portion (131, 132) and the n-dopedsemiconductor region 134 of each temperature control device (90, 142,131, 132, 140, 133, 134, 144, 92). The majority charge carriers areholes in the at least one p-doped semiconductor portion (131, 132), andare electrons in the at least one n-doped semiconductor region 134. Theheat is further transferred to the at least one first metal contact via90 and the at least one second metal contact via 92. Because of thethermal coupling between the at least one first metal semiconductoralloy region 140 and the optoelectronic device 160, the heat is alsotransferred from the optoelectronic device 160 to the at least one firstmetal semiconductor alloy region 140 as the at least one first metalsemiconductor alloy region 140 is cooled. Therefore, there is a net heattransfer from the optoelectronic device 160 to the at least one firstmetal contact via 90 and the at least one second metal contact via 92.The heat that is transferred to the at least one first metal contact via90 and the at least one second metal contact via 92 may further betransferred to a heat sink (not shown) through metallic interconnectstructures embedded in the interconnect-level dielectric material layer80.

If the electrical current flows in the reverse current direction, themajority charge carriers diffuse toward the interface with one of the atleast one first metal semiconductor alloy region 140 and away from theinterface with one of the at least one second metal semiconductor alloyregion 142 and the at least one third metal semiconductor alloy region144 within the p-doped semiconductor portion (131, 132) and the n-dopedsemiconductor region 134 of each temperature control device (90, 142,131, 132, 140, 133, 134, 144, 92). The transferred heat accumulates atthe at least one second metal semiconductor alloy region 142 and the atleast one third metal semiconductor alloy region 144. Because of thethermal coupling between the at least one first metal semiconductoralloy region 140 and the optoelectronic device 160, the heat is furthertransferred from the at least one first metal semiconductor alloy region140 to the optoelectronic device 160 as the at least one first metalsemiconductor alloy region 140 is heated by heat transfer. Therefore,there is a net heat transfer from the at least one first metal contactvia 90 and the at least one second metal contact via 92 to theoptoelectronic device 160. The heat may be transferred from a heat sink(not shown) to the at least one first metal contact via 90 and the atleast one second metal contact via 92 through metallic interconnectstructures embedded in the interconnect-level dielectric material layer80, then subsequently transferred to the optoelectronic device 160.

Therefore, by reversing the direction of flow of the electrical current,the direction of heat transfer may be reversed. Further, by adjustingthe magnitude of the electrical current, the amount of heat transfer maybe regulated. Typically, the material of the low-k dielectric materialportion 150 has a lower thermal conductivity than the material of theburied insulator layer 20, thereby increasing the thermal isolation ofthe at least one first metal semiconductor alloy portion 140 and theoptoelectronic device 160 from the handle substrate 10.

The first semiconductor device may be operated with a feedback mechanismfor performance of the optoelectronic device 160. For example, theperformance of the optoelectronic device 160 may be monitored duringoperation. Based on the monitored performance level of theoptoelectronic device, a direction of the electrical current ormagnitude of the electrical current may be manipulated to heat or coolthe optoelectronic device, thereby reducing deviation in the performanceof the optoelectronic device 160 from a target performance level.

Referring to FIG. 17, a third exemplary semiconductor structureaccording to a third embodiment of the present invention is derived fromthe second exemplary semiconductor structure by forming a substantiallyintrinsic lower semiconductor portion 30 and a substantially intrinsicupper semiconductor portion 138 in each temperature control device. Avertically abutting pair of a substantially intrinsic lowersemiconductor portion 30 and a substantially intrinsic uppersemiconductor portion 138 is herein referred to as a substantiallyintrinsic semiconductor portion (30, 138). Thus, each of the at leastone temperature control device may include the substantially intrinsicsemiconductor portion 30.

The substantially intrinsic semiconductor portion (30, 138) is formedbetween a p-doped semiconductor portion (131, 132) and an n-dopedsemiconductor portion (133, 134) of the at least one temperature controldevice (90, 142, 131, 132, 140, 30, 138, 133, 134, 144, 92). Thesubstantially intrinsic semiconductor portion (30, 138) may have thesame composition as the semiconductor waveguide 136. The substantiallyintrinsic semiconductor portion (30, 138) vertically abuts the firstmetal semiconductor alloy region 140 of the at least one temperaturecontrol device (90, 142, 131, 132, 140, 133, 134, 144, 92). In one case,the p-doped semiconductor portion (131, 132) and the n-dopedsemiconductor portion (133, 134) may be not abut each other, and arelaterally separated by the substantially intrinsic semiconductor portion(30, 138). In another case, the p-doped semiconductor portion (131, 132)and the n-doped semiconductor portion (133, 134) may abut each other andthe substantially intrinsic semiconductor portion (30, 138).

A low-k dielectric material portion 150, an optoelectronic device 160,an interconnect-level dielectric material layer 80, at least onecompound semiconductor via 85, at least one first metal contact via 90,and at least one second metal contact via 92 may be formed in the samemanner as in the second embodiment. Within the collective volume of theat least one substantially intrinsic semiconductor portion (30, 138) andthe at least one first metal semiconductor alloy region 140, the currentflows primarily through the at least one first metal semiconductor alloyregion 140. Therefore, the addition of the at least one substantiallyintrinsic semiconductor portion (30, 138) does not change the currentpath in a substantial manner relative to the current path in the secondembodiment. The at least one temperature control device (90, 142, 131,132, 140, 30, 138, 133, 134, 144, 92) may be operated in the same manneras in the second embodiment to control the temperature of theoptoelectronic device 160 and to regulate the performance of theoptoelectronic device 160.

Referring to FIG. 18, a fourth exemplary semiconductor structureaccording to a fourth embodiment of the present invention is shown. Thefourth exemplary semiconductor structure is derived from the secondexemplary semiconductor structure of FIGS. 13A and 4B by omitting thesteps corresponding to FIGS. 14A and 5B in the processing sequence.Specifically, application of a photoresist 147, patterning of thephotoresist 147, and transfer of the pattern in the photoresist 147 intoan exposed portion of the buried insulator layer 20 are omitted in thethird embodiment.

Instead of patterning the buried insulator layer 20, a lower portion ofan interconnect-level dielectric material layer 80 is formed over the atleast one temperature control device (90, 142, 131, 132, 140, 133, 134,144, 92) and the semiconductor waveguide 136. The top surface of thelower portion of the interconnect-level dielectric material layer 80 isplanarized by employing a self-planarizing material for the lowerportion of the interconnect-level dielectric material layer 80 and/or byperforming a planarization processing step such as chemical mechanicalplanarization or a recess etch. An optoelectronic device 160 is formedover the top surface of the lower portion of the interconnect-leveldielectric material layer 80. The optoelectronic device 160 may be thesame as in the second embodiment, and may overlie the at least one firstmetal semiconductor alloy region 140 and a portion of the semiconductorwaveguide 136. An upper portion of the interconnect-level dielectricmaterial layer 80 is formed over the optoelectronic device 160. Thelower portion and the upper portion of the interconnect-level dielectricmaterial layer 80 may comprise the same material as in the secondembodiment. At least one compound semiconductor via 85, at least onefirst metal contact via 90, and at least one second metal contact via 92may be formed in the same manner as in the second embodiment. The atleast one temperature control device (90, 142, 131, 132, 140, 133, 134,144, 92) may be operated in the same manner as in the second embodimentto control the temperature of the optoelectronic device 160 and toregulate the performance of the optoelectronic device 160.

Referring to FIG. 19, a fifth exemplary semiconductor structureaccording to a fifth embodiment of the present invention is derived fromthe second exemplary semiconductor structure by omitting formation of atleast one compound semiconductor via 85.

Referring to FIG. 20, a sixth exemplary semiconductor structureaccording to a sixth embodiment of the present invention is derived fromthe second exemplary semiconductor structure at a step corresponding toFIGS. 14A and 5B by removing the photoresist 147 and employing anon-conformal deposition process to form a low-k dielectric materialportion 150. The material of the low-k dielectric material portion 150may be the same as in the second embodiment. The non-conformal propertyof the deposition process employed to form the low-k dielectric materialportion 150 deposits a low-k dielectric material over narrow portions ofthe of the semiconductor structures above the top surface of the buriedinsulator layer 20, i.e., between the at least one temperature controldevice (90, 142, 131, 132, 140, 133, 134, 144, 92) and the semiconductorwaveguide 136. Thus a cavity 152 is formed within the low-k dielectricmaterial portion 150.

Referring to FIG. 21, processing steps corresponding to FIGS. 15A-7B ofthe second embodiment are performed on the sixth exemplary semiconductorstructure. The cavity 152 may be under vacuum after processing, or maybe filled with air or a gas. The cavity 152 has a dielectric constantthat is substantially equal to 1.0. The cavity 152 has a lower thermalconductivity than the material of the buried insulator layer 20, therebyincreasing the thermal isolation of the at least one first metalsemiconductor alloy portion 140 and the optoelectronic device 160 fromthe handle substrate 10. The at least one temperature control device(90, 142, 131, 132, 140, 133, 134, 144, 92) may be operated in the samemanner as in the second embodiment to control the temperature of theoptoelectronic device 160 and to regulate the performance of theoptoelectronic device 160.

Referring to FIG. 22, a seventh exemplary semiconductor structureaccording to a seventh embodiment of the present invention is shown.FIG. 111 is a top-down view of selected elements including p-dopedsemiconductor portions (131, 132), n-doped semiconductor portions (133,134), first metal semiconductor alloy regions 140, second metalsemiconductor alloy regions 142, third metal semiconductor alloy regions144, first metal contact vias 90, second metal contact vias 92, and asemiconductor waveguide 136. The location of the optoelectronic device160 is shown in a broken line. A vertical cross-sectional view along theplane Z-Z′ is the same as FIG. 15A.

Each of the first metal semiconductor alloy regions 140 is locatedwithin a first annulus. Each of the p-doped semiconductor portions (131,132) and n-doped semiconductor portions (133, 134) is located within asecond annulus which encloses and abuts the first annulus. Each of thesecond metal semiconductor alloy regions 142 and the third metalsemiconductor alloy regions 144 is located within a third annulus whichencloses and abuts the second annulus. The p-doped semiconductorportions (131, 132), the n-doped semiconductor portions (133, 134), thefirst metal semiconductor alloy regions 140, the second metalsemiconductor alloy regions 142, and the third metal semiconductor alloyregions 144 constitute two temperature control devices (90, 142, 131,132, 140, 133, 134, 144, 92) between which a semiconductor waveguide 136is located. An optoelectronic device 160 overlies portions of the twotemperature control devices (90, 142, 131, 132, 140, 133, 134, 144, 92)and the semiconductor waveguide 136 as in the second embodiment. The twotemperature control devices (90, 142, 131, 132, 140, 133, 134, 144, 92)may be operated in the same manner as in the second embodiment tocontrol the temperature of the optoelectronic device 160 and to regulatethe performance of the optoelectronic device 160.

In general, topological variations may be performed to the at least onetemperature control devices (90, 142, 131, 132, 140, 133, 134, 144, 92and optionally 30 and 138) to any of the exemplary semiconductorstructures described above. Further, additional temperature controldevices having a similar structure may be added to any of the exemplarysemiconductor structures described above.

While the invention has been described in terms of specific embodiments,it is evident in view of the foregoing description that numerousalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, the invention is intended to encompassall such alternatives, modifications and variations which fall withinthe scope and spirit of the invention and the following claims.

What is claimed is:
 1. A method of forming a semiconductor structurecomprising a temperature control device and an optoelectronic device,said method including: forming a top semiconductor portion by patterninga top semiconductor layer of a semiconductor-on-insulator substrate,wherein an entirety of top semiconductor portion has a first thicknessthroughout upon formation and comprises: a primary top semiconductorportion having a semiconductor portion width; a pair of first laterallyprotruding top semiconductor portions having a greater width than saidsemiconductor portion width; and a pair of second laterally protrudingtop semiconductor portions having a greater width than saidsemiconductor portion width; forming a p-doped semiconductor in each ofsaid pair of first laterally protruding top semiconductor portion and ann-doped semiconductor portion in each of said pair of second laterallyprotruding top semiconductor portions; forming a metal semiconductoralloy region directly on said p-doped semiconductor portion and saidn-doped semiconductor portion, wherein said p-doped semiconductorportion, said n-doped semiconductor portion, and said metalsemiconductor alloy region constitute a portion of a temperature controldevice; forming a current conduction path configured to pass currentfrom said p-doped semiconductor portion, through said metalsemiconductor alloy region, and to said n-doped semiconductor portion orfrom said n-doped semiconductor portion, through said metalsemiconductor alloy region, and to said p-doped semiconductor portion;and forming an optoelectronic device comprising a semiconductormaterial, configured to manipulate electromagnetic radiation, andthermally coupled to said temperature control device.
 2. The method ofclaim 1, wherein said optoelectronic device overlies said metalsemiconductor alloy region.
 3. The method of claim 1, further comprisingremoving a portion of a buried insulator layer underneath a sub-portionof said p-doped semiconductor portion and a sub-portion of said n-dopedsemiconductor portion to form a trench in said buried insulator layer.4. The method of claim 3, further comprising filling said trench with alow dielectric constant (low-k) material having a dielectric constantless than 3.0, wherein said optoelectronic device is formed over saidlow-k material.
 5. The method of claim 4, further comprising forming acavity laterally abutting a remaining portion of said buried insulatorlayer by removing said low-k material selective to said remainingportion of said buried insulator layer.
 6. The method of claim 1,further comprising a shallow trench isolation structure contacting a topsurface of a buried insulator layer within saidsemiconductor-on-insulator substrate.
 7. The method of claim 1, whereinan entirety of said top semiconductor portion is single crystalline. 8.The method of claim 1, further comprising forming a pair of recessedline trenches having a recess depth within said primary topsemiconductor portion, wherein said recess depth is less than said firstthickness.
 9. The method of claim 8, wherein said optoelectronic devicecomprises a waveguide having a uniform width, and said waveguide isformed between said pair of recessed line trenches.
 10. The method ofclaim 8, wherein sidewalls of said pair of first laterally protrudingtop semiconductor portions and sidewalls of said pair of secondlaterally protruding top semiconductor portions are physically exposedto said pair of recessed line trenches.
 11. The method of claim 8,wherein said p-doped semiconductor portion is formed within one of saidpair of first laterally protruding top semiconductor portions and asub-portion of said primary top semiconductor portion that underlies oneof said pair of recessed line trenches, and said n-doped semiconductorportion is formed within one of said pair of second laterally protrudingtop semiconductor portions and another sub-portion of said primary topsemiconductor portion that underlies said one of said pair of recessedline trenches.
 12. The method of claim 8, wherein said metalsemiconductor alloy region is formed on a bottom surface of one of saidpair of recessed line trenches.
 13. The method of claim 1, wherein saidp-doped semiconductor portion and said n-doped semiconductor portionlaterally contact each other upon formation and have a p-n junctiontherebetween.
 14. The method of claim 13, further comprising forming awaveguide having a uniform width, wherein said waveguide is laterallyspaced from said p-doped semiconductor portion and said n-dopedsemiconductor portion.
 15. The method of claim 1, further comprising:forming another metal semiconductor alloy region on said p-dopedsemiconductor portion concurrent with formation of said metalsemiconductor alloy region; and forming yet another metal semiconductoralloy region on said n-doped semiconductor portion concurrently withformation of said metal semiconductor alloy region.
 16. The method ofclaim 15, wherein each of said another metal semiconductor alloy regionand said yet another metal semiconductor alloy region is spaced fromsaid metal semiconductor alloy region.
 17. The method of claim 1,wherein said optoelectronic device comprises a waveguide having auniform width and formed by patterning said top semiconductor layer, andsaid method further comprises suspending said waveguide above a handlesubstrate of said semiconductor-on-insulator substrate by removing aportion of a buried insulator layer from underneath said waveguide. 18.The method of claim 17, further comprising depositing a dielectricmaterial employing a non-conformal deposition method over said waveguideafter suspending said waveguide, whereby a cavity is formed within aportion of said deposited dielectric material underneath said waveguide.